Preparation of boron hydrides



United States Patent Ofi 3,109,710 PREPARATION OF BORON HYDRIDES James L. Boone, Los Angeles, Calif., assignor to American Potash & Chemical Corporation, a corporation of Delaware No Drawing. Filed Dec. 15, 1958, Ser. No. 780,258 3 Claims. (Cl. 23-204) This invention relates in general to the preparation of hexaborane and pent-aborane-9 and more particularly to the preparation of hexaborane and pentaborane-9 by the reaction of tetraborane or pentaborane-ll with It is an object of this invention to provide for the preparation of hexaborane and pentaborane-9 by the reaction of B5Hu or B4H10 Further objects and advantages of the invention, if not specifically set forth, will become apparent during the course of the description which follows.

Generally, it has been found that B H and B H may be converted to B H and B H by reaction with [(CH N] BH at relatively low temperature. The reagents conveniently may be mixed at 78 C., but reactions leading to volatile boranes are very slow under such conditions. Reasonable yields of these compounds are obtained during slow warming to C.; and by suitable control of the time and temperature, the reactions can be effected in periods which are greatly reduced from those reported below. When either B H or B H are used, both B H and B H are obtained as products.

Examples of the process of this invention are set forth below for illustrative purposes, but these are not to be interpreted as imposing limitations on the scope of the invention other than as are set forth in the appended claims.

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2 The B6H10 was identified by its MP. (-66 to 65 c 5.95 B(OH) per B H (calcd., 14.0 and 6.00).

EXAMPLE II The partial conversion of B H to B H and B -H was carried out by the use of 1.88 mmoles of 3 H (plus 0.130 mmole B H impurity) with 0.748 mmole of [(CH N] BH. After 17 hours at 78 C., the mixture was warmed to 0 C. during 9 hours. The products obtained are shown in Table B, vide infra, which table also includes the results of the secondary treatment of the non-volatile oily-gum residue with additional samples of B H These secondary treatments show that the residue acts in a catalytic manner in converting successive samples of B H to useful yields of B H It therefore appears possible to accomplish a large amount of B H conversion to B H by means of a small amount of initially necessary [(CH N] BH. Only in the first experiment of Table B was there any appreciable evolution of H (0.045 mole).

As stated earlier, a convenient operating range is -78 C. (the temperature of a Dry Ice bath) to 0 C. However, higher temperatures may be suitable if proper control over reagent contact time is exercised. The maximum usable temperature is that at which the reagent B 11 or the product B H would decompose faster than it could be introduced or removed from the system.

The boron hydrides produced in this fashion are useful as pyrophoric fuel components and also may be used as reigniters in the event of jet flameouts.

Obviously, many modifications and variations may be made Without departing from the spirit and scope of this invention, and therefore only such limitations should be imposed as are indicated in the appended claims.

Table B PENTABORANE-ll CONVERSION Experiment NO. 1 2 3 4 5 Treatment of residue from prior experiment 8 days at Room temp., Left 3 da Left 5 days room temp; 27 days. at 0 0. at 0 C. volatiles removed. New B51311- 1. 75 322 0. 421 0. 814 0. 840. ResiducdhH contact conditions (See text)-.- Warmed from Warmed, --78 6.5 hours at 3.0 ours at 78 to 20 to 20 0., 0 0. 0 C. O. in 6.5 4.0 hrs. hrs. Percent BsHn consume 100 34 98 69. Yields of other boranes, given as percent B in BsHn consumed:

BZHQ- 11. 1 22. 1 25. 4 32. 8 34. 4 BAHm 18. 9 31.0 19.7 14. 9 11. 6 BsHa 1 37. 0 l4. 5 13. 3 9. 7 5. 7 BaHm 8. 4 30. 7 l9. 5 16. 5 22. 4 (CHahNBzHs 4. 1 l. 9

Total 79. 5 100. 2 78. 0 74. 0 74. 0

1 Corrected for BsHn impurity in the BsHn sample, the amount of which also was corrected for 13 11.

EXAMPLE I Table A .031. B 119 0.425, 27.4%. .183, 4. 7%. BeHm 0.087, 6.7%. .228(recovcred). (CHs)2NBzH5 0.125, 3.2%.

I claim:

1. A process which comprises reacting [(CH N] BH with B H said reaction being carried out for a period of time and at a temperature sufficient to form a reaction product mixture containing B H and B H said temperature being within the range of from -78 C. up to about 0 C., and then separating at least one of B H and B H from said reaction product mixture.

2. A process which comprises reacting [(CH N] BH with B H said B H being employed, relative to said [(CH N] BH, in a molar ratio greater than one and said reaction 'being carried out for a period of time and at a temperature sufficient to form a reaction product 3 mixture containing B H and B H said temperature being within the range of from 78 C. up to about 0 C., and then separating at least one of B H and B H from said reaction product mixture.

3. A process which comprises reacting [(CH N] BH with B H said reaction being carried out for a period of time and at a temperature suflicient to form a reaction product mixture containing B H and B H said temperature being within the range of from -78 C. up

4 OTHER REFERENCES Boone et al.: Journal of the American Chemical Society, vol. 80, page 1519-1520 (Mar. 20, 1958).

Wibeng: Berichte, vol. 77, part A, page 89 (1944).

Burg et al.: Journal of the American Chemical Society, vol. 13, pages 953-957 (1951).

Burg et 211.: Journal of the American Chemical Society, v01. 55, page 4011-4012 (1933).

Burg: Journal of the American Chemical Society,

to about 0 C., and then separating B H from said 10 vol. 79, pages 2129-2132 (1957).

reaction product mixture.

Stone: Quarterly Reviews, vol. 9, page 193 (1955). 

1. A PROCESS WHICH COMPRISES REACTING ((CH3)2N)2BH WITH B4H10, SAID REACTION BEING CARRIED OUT FOR A PERIOD OF TIME AND AT A TEMPERATURE SUFFICIENT TO FORM A REACTION PRODUCT MIXTURE CONTAINING B6H10 AND B5H9, SAID TEMPERATURE BEING WITHIN THE RANGE OF FROM -78*C. UP TO ABOUT 0*C., AND THEN SEPARATING AT LEAST ONE OF B6H10 AND B5H9 FROM SAID REACTION PRODUCT MIXTURE. 